Application of additional dose of N could sustain rice yield and maintain plant nitrogen under elevated ozone (O3) and carbon dioxide (CO2) condition.

Introduction: Global food security is challenged by the increasing levels of air pollutants like ozone (O₃) through their impacts on crop productivity. The present study was conducted to quantify the interactive effect of elevated ozone (O₃) and carbon dioxide (CO₂), on different rice varieties in northern India. Methods: An experiment was conducted in Genetic H field, Environment science, IARI for two consecutive years (2020 and 2021) during the kharif season, to quantify the impact of elevated O₃ and CO₂ interaction on productivity, and plant N in three rice varieties (Pusa basmati 1121, Nagina 22, IR64 Drt1) under different nitrogen (N) management practices. Rice crop was grown in Free Air Ozone-Carbon dioxide Enrichment rings (FAOCE) rings with two levels of O₃ (elevated 60 ±10ppb and ambient) and two levels of CO₂ (elevated, 550±25 ppm and ambient) concentration and their interaction with two N fertilizer treatments i.e., 100% RDN (recommended dose of N) and 125% RDN. Results and discussion: Elevated O₃ significantly decreased physiological parameters like photosynthesis rate, stomatal conductance and transpiration rate of the crop. Grain yield reduced by 7.2-7.5%, in Pusa Basmati 1121 and from 6.9-9% in IR64 Drt1 varieties in elevated O₃ treatment as compared to ambient treatment. Yield reduction in Nagina 22 variety was not significant in elevated O₃ treatment. Elevated CO₂ concentration of 550 ppm was able to fully compensate the yield loss in Nagina 22 variety and partially compensate (3.9-8.0%) in Pusa Basmati 1121 and IR64 Drt1 varieties. Grain N concentration in rice varieties decreased by 10.8-14.7% during first year and by 7.8-20.6% during second year in elevated O₃ plus CO₂ interaction treatment than ambient. Grain N uptake also decreased (13.2-17.1% in first year and 4.5-22.8% in second year) in elevated O₃ plus CO₂ interaction treatment as compared to ambient. Application of additional 25% of recommended dose of N improved grain N concentration, grain N uptake as well as available N of soil as compared to 100% RDN treatment in elevated O₃ plus CO₂ interaction treatment. Additional 25% N dose could help in sustaining rice productivity and quality under elevated O₃ and CO₂ condition. [ABSTRACT FROM AUTHOR]